This non-provisional application claims priority under 35 U.S.C. 119(a) on Patent Application No. 2003-43564 filed in Korea on Jun. 30, 2003, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to an organometallic precursor composition and a method of forming a metal film or pattern using the same. More specifically, the present invention relates to a composition comprising (i) an organometallic precursor containing a hydrazine compound coordinating to a central metal thereof and (ii) an organometallic compound of a main group metal and a method of forming a metal film or pattern using the composition.
2. Description of the Related Art
A metal pattern to be formed on a substrate continues to get smaller in accordance with the recent trend of an increase in the degree of integration and a decrease in the size of electronic devices, such as integrated circuits (IC) and Liquid crystalline displays. Usually, metal patterns are formed on a substrate through a photolithography process using a photoresist and generally include the steps of a) forming a metal layer on a substrate via a chemical vapor deposition process (CVD process), a plasma deposition process or an electrical plating process; b) coating a photoresist on the metal layer; c) exposing the coated photoresist to UV-radiation under a photomask having a pattern; d) developing the photoresist layer to obtain a patterned photoresist layer; and e) etching the metal layer under the pattern of the photoresist with, for example, a reactive ion-etching process to form a metal pattern on the substrate. Since the photolithography process involves many complicated steps and requires the use of a large amount of fine chemicals such as expensive photoresist compositions and etchants, it is undesirable in terms of cost and environmental protection. Especially, in the photolithography process, there are many steps such as depositing or etching that should be conducted at a high temperature and/or high pressure, and thus, the operational costs become very high. Also, metal vapor diffusion into the substrate, which frequently occurs under a high temperature process, brings about a malfunction or defect in the final electronic device. On the other hand, for a flexible display or a TFT-LCD to achieve a high quality picture and a large-scaled screen, technology is urgently required for developing a gate dielectric layer of high quality and a source/drain electrode region with low resistance. Under these circumstances, many studies have been made on the formation of a metal film or pattern through a simple procedure at a relatively low temperature.
As an alternative technology for the photolithography process, soft-lithography and ink-jet printing draw attention because they form a very fine pattern on a substrate through relatively simplified procedures requiring low operational costs. However, these two technologies still have the problems that a film or a pattern obtained should be heat-treated, or additionally oxidized or reduced at a high temperature in order for the film or pattern thus obtained to have a lower resistivity. But considering the materials currently used for the substrate, a heat treatment at high temperatures is not advantageous so there remains a need to develop a novel ink which allows the formation of a metal pattern with high durability and high conductivity at a high resolution via a more simplified process requiring a low temperature.
In this regard, IEEE Transactions on component Hybrids and Manufacturing Technology 12(4), 1987 (“Liquid ink-jet printing with MOD inks for hybrid microcircuits”, Teng, K. F. and Vest, R. W.) discloses organometallic compounds that can be thermally decomposed at low temperatures and converted into metals or metal oxides, i.e., so-called metallo-organic decomposition (MOD) compounds, and U.S. Pat. No. 5,882,722 discloses a technology of forming a metal film or pattern using these MOD compounds. However, this technology has the drawback that the metal film or pattern thus formed tends to melt before thermal-decomposition so it is very difficult to secure the required thickness of the metal film or pattern. Also, the resistivity of the metal film or pattern thus obtained is quite high. To avoid these problems, multiple coating has been proposed as an alternative, but it is not preferable because multiple coating entails many complicated steps and high costs. U.S. Pat. No. 5,173,330 discloses a method using organometallic precursors to form a thin metal film or nuclei that is normally used in an electrolytic plating process but this method is undesirable because of the low conductivity of the obtained film or pattern. Further, U.S. Pat. Nos. 4,186,244 and 4,463,030 disclose a process of forming a metal film at a low temperature by using silver (Ag) powder and a surfactant wrapping the silver powder. However, this process is disadvantageous in that, after formation, the metal film should be exposed to a high temperature of 600° C. or higher in order to remove the surfactant. If the metal film is not exposed to this high temperature, the specific resistivity of the metal film becomes undesirably high because of organic materials remaining on the metal film.
In addition, U.S. Pat. No. 6,036,889 discloses a process of forming a highly conductive metal pattern with a specific resistivity of about 3.0 μΩcm−1 on a polymer substrate at the low temperatures of 350° C. or lower using a mixture of MOD compounds, metal flakes and metal colloid. In the mixture, the MOD compounds lowers the required temperature for the heat treatment and facilitates the formation of a coating on the substrate, while the metal flakes promote the solidification of a precursor so as to prevent the MOD compounds from melting before the formation of a metal film. This process attempts to overcome the problems in the prior art by using a multi-component mixture, in which one compound helps avoid the problems of other compounds so as to obtain a metal pattern with excellent properties. However, there is a limitation in improving the properties of the metal pattern because this process does not address the fundamental problems in the prior art and every component in the mixture has its upper limit in its content. Hence, it is impossible to form a metal film or pattern with a high conductivity corresponding to a pure metal at a temperature of 250° C. or lower through this process.
On the other hand, as a highly integrated circuit is developed, an extremely fine metal pattern is required. In such a pattern, poor adhesion or surface morphology may result in serious problems such as disconnection of the circuit. Thus these characteristics are important.
Therefore, there remains a need to develop a method of forming a metal film or pattern with high conductivity corresponding to that of a pure metal and a desired thickness via a simple procedure using a relatively low temperature, wherein the film or pattern thus obtained shows both an excellent adhesion and a good surface morphology.
The present inventors have conducted extensive studies and have found that a highly conductive metal film or pattern having a specific resistivity of 2.5 to 3.0 μΩcm−1, an excellent adhesion and a good surface morphology can be obtained through a simple procedure at a relatively low temperature, by using a composition comprising (i) an organometallic precursor containing a hydrazine compound coordinating to a central metal thereof and (ii) an organometallic compound of a main group metal, such as Si, Ge, Sn or Bi.